exports.$ = (id) => {
    return document.getElementById(id);
}
exports.formatDuration = (time) => {
    const minutes = "0" + Math.floor(time / 60);
    const second = "0" + Math.floor(time - minutes * 60);
    //截取后两位,例如"030",则截取"30";如果是"06",则依然截取"06"
    return minutes.substr(-2) + ":" + second.substr(-2);
}